BMI has been recommended for evaluating overweight and obesity in children and adolescents in the clinical setting. Definitions of overweight and obesity are based on percentile cutoff points. There are both strengths and limitations of BMI for this use. The strengths include the fact that BMI is cheap and relatively easy to use. The weaknesses include the fact that BMI percentiles are not widely used, and categorization of BMI percentiles may not adequately define risk of comorbid conditions. In addition, percentiles are not optimal for stratifying children and adolescents with very high BMI. Alternatives to the use of BMI and BMI percentiles include waist circumference to evaluate regional fat deposition and replacement of percentiles with z scores. Despite limitations, BMI and BMI percentiles have great utility in the clinical setting and the potential to be even more useful as BMI is used more frequently and more appropriately by primary care providers. Additional research on alternatives or adjuncts to BMI is needed.